Asexual vs. Sexual Reproduction

Asexual Reproduction Asexual reproduction: production of offspring by 1 parent New cells are IDENTICAL to parent cell

Asexual Reproduction Advantages Takes less time and energy Don’t have to find a mate; takes only 1 parent More likely to survive in a stable environment

Sexual Reproduction Sexual reproduction: production of offspring by combining genetic information from 2 parents

More likely to survive in a changing environment Sexual Reproduction Advantages Genetic variation More likely to survive in a changing environment

Chromosomes

DNA & Chromosome Structure DNA is a long molecule and unwound it is called chromatin DNA can wind up to become chromosomes Chromatin  chromosome right before cell division

Chromosome Structure Uncopied chromosome Copied chromosome contains 2 sister chromatids Sister chromatids are IDENTICAL to one another Held together by a centromere

Chromosome Number Each species has a specific number of chromosomes Humans have 46 chromosomes or 23 pairs Each pair is called a homologous pair 1 from mom, 1 from dad Homologous chromosomes carry the same genes

Chromosome Number Cells that have a full set of chromosomes are diploid cells (2N). All body (somatic) cells are diploid. Cells that have a half set of chromosomes are haploid cells (N). All gametes (sperm and egg) are haploid.

Cell Division

What do you see happening? Lung cell: http://labs.bio.unc.edu/Salmon/mitosis/newnewtdic.mov Animation: http://www.youtube.com/watch?v=VlN7K1-9QB0 What must happen before the cell divides?

The Cell Cycle Cell cycle is the life cycle of a cell Broken into 2 phases: Interphase M phase

Events of the Cell Cycle Interphase is made up of 3 sub-phases: G1: cell grows S: DNA copies G2: cell grows and prepares for division

Events of the Cell Cycle M phase is made of 2 sub-phases: Division of the nucleus & DNA Cytokinesis: division of the cytoplasm

Events of the Cell Cycle

Interphase (before Mitosis) Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Cell growth DNA replicates Anaphase Nuclear envelope reforming

Prophase Chromosomes become visible Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Chromosomes become visible Centrioles separate and spindle fibers form Nuclear envelope disappears Telophase Individual chromosomes Anaphase Nuclear envelope reforming

Metaphase Metaphase Chromosomes line up in the middle Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Chromosomes line up in the middle Spindle fibers attach at the centromere of each chromosome Nuclear envelope reforming

Anaphase Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Nuclear envelope reforming Sister chromatids separate and move towards opposite ends of the cell

Telophase Chromatids are at opposite ends of cell Section 10-2 Spindle forming Centrioles Chromatids are at opposite ends of cell Nuclear envelope reforms Nuclear envelope Chromatin Centromere Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Nuclear envelope reforming

Cytokinesis (after Mitosis) Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Cytoplasm pinches and divides in half Two identical daughter cells are formed Nuclear envelope reforming

Cell Size and Cell Cycle

Why do cells divide? Too much demand on the cells’ DNA The larger a cell becomes, the more demand the cell places on its DNA. Difficult to get nutrients and wastes across the cell membrane A larger cell has trouble moving substances from the membrane to all parts of the cell.

DNA “Overload” Cells only have so much DNA. When they get bigger, they don’t make more DNA. So if cells grew indefinitely, the DNA wouldn’t be able to meet all its needs.

Exchanging Materials How fast things can be exchanged depends on the surface area of a cell. How fast waste is made and nutrients are needed depends on volume of a cell. As cells get bigger, ___________ increases faster than __________ ________. volume surface area

So…what do cells do? Before a growing cell gets too large, it will divide. This creates 2 daughter cells. The process is called cell division.

The Cell Cycle Cell cycle: the life cycle of the cell as they grow and divide Made up of 2 large phases: Interphase M phase

Regulating the Cell Cycle In humans, nerve cells and muscle cells do not continue to divide after they have developed. That is why spinal cord injuries are not repaired. Other cells divide rapidly throughout life. Example: skin cells, hair cells, and cells in the bone marrow that make blood cells

Cell Cycle Regulators Internal regulators: respond to events inside the cell Example: cell cycle only proceeds when certain events have occurred Cyclin: a group of proteins that regulates the timing of the cell cycle within cells The sample is injected into a second cell in G2 of interphase. A sample of cytoplasm is removed from a cell in mitosis. As a result, the second cell enters mitosis.

Cell Cycle Regulators External regulators: respond to events outside the cell Example: Growth regulators are important in wound healing.

Fertilization & Differentiation http://10.11.251.1/?p=5af6a73f-3bcf-11e1-8cac-842b2b0824aa

Fertilization Fertilization: joining of egg and sperm Fertilization restores the diploid number! 1st cell is called a zygote

What next? After fertilization, mitosis continues to produce more cells as you grow. Aging occurs because mitosis slows down Cells continue to die but are not able to be replaced as quickly.

Differentiation of cells Cells become specialized to make different types of cells.

Differentiation of cells Different types of cells make different proteins because different combinations of genes are active in each type.

Why do cells divide? Multicellular organisms use… Mitosis to grow and heal Meiosis to sexually reproduce

Differentiation and Stem Cells What do you know about stem cells? http://www.youtube.com/watch?v=2-3J6JGN-_Y

Missouri Stem Cell Research and Cures Initiative In 2006, Missouri passed the Stem Cell Research and Cures Initiative. This allowed any stem cell research and therapy in Missouri that is legal under federal law, including somatic cell nuclear transfer to produce human embryos for stem cell production it prohibits cloning or attempting to clone a human being Do you agree or disagree with this initiative?

Control of the Cell Cycle & Cancer

Cell Division and Cancer DNA codes for proteins that regulate cell division. If DNA is mutated, cell division can occur out of control. Cancer: uncontrolled cell division

Mutations in DNA can cause cancer Possible mutagens (causes) High energy radiation (UV & X-rays) Chemicals High temperatures Mistakes in DNA replication Viruses Other environmental factors

Cancer cells can produce malignant tumors

Skin Cancer Application How does cancer relate to the cell cycle?

Accumulation of mutations lead to cancer Chromosomes mutation 1 2 3 4 mutations Normal cell Malignant cell Figure 11.18B

Dear 16 Year Old Me… http://www.youtube.com/watch?v=_4jgUcxMezM

Different types of Cell Divisions Mitosis Meiosis Function Number of chromosomes in parent cell Number of daughter cells after cell division Number of chromosomes in each daughter cell Type of cell produced Number of times cell divides Difference in DNA in parent and daughter cells

Different types of Cell Divisions Mitosis Meiosis Two daughter cells are formed from each original cell Four daughter cells are formed from each original cell Replication of chromosomes occurs Cells with reduced chromosome numbers are formed Cells with the same chromosome number as original cell are formed Results in forming egg or sperm cells Results in forming somatic (body) cells Each original cell divides only once Each original cell divides twice Chromosomes move to the center of the cell

Karyotypes

Karyotyping Karyotyping: a process used to look at an individual’s chromosomes (can be done before birth)

Chromosome number A human has 23 pairs of chromosomes Chromosomes 1-22 are called autosomes 23rd pair is the sex chromosomes

Sex Chromosomes The X chromosome The Y chromosome Large in size Carries many genes on it Must have 1 X chromosome to live The Y chromosome Small in size Carries few genes that cause development into males Only males have a Y chromosome

Sex Chromosomes X and Y do NOT refer to the shape of the chromosome. A normal female is XX. A normal male is XY.

Genetic Disorders Normal cells have pairs of chromosomes. If a cell has an extra copy of one chromosome, it is called trisomy. If a cell is missing one copy of a chromosome, it is called monosomy.